What does 'See some light' mean?

Get whatever light exposure you can - it doesn’t need to be bright! More importantly, make sure to avoid darkness, and remember not to wear your sunglasses.

When flying:Raise the window shade if it’s light outside, turn on the overhead light, and turn on the TV or use your laptop or tablet.

Why do I need to expose myself to light?

Light is the most powerful factor in resetting circadian rhythms and reducing jet lag. The effects of light vary by time of day, however, and it’s important to maximize light exposure to support the overall plan and make sure you’re not exposing yourself to darkness, which will derail the plan.

What will happen to my jet lag if I don’t get some light at this time?

The light timing is planned to help reset your circadian rhythm as quickly as possible. If you don’t see any light at this time, it will take longer to overcome your jet lag. As long as you are exposed to daylight or normal indoor light levels, you will be supporting the plan. Remember not to wear sunglasses at this time — that would block the benefits of light.

The science

Light is the most important factor in resetting your circadian rhythm — the disruption of the light-dark cycle is in fact what causes jet lag in the first place. Light resets our circadian rhythm to 24 hours each and every day, and is detected by special photoreceptors in the eye.

Light can shift the clock earlier (called an advance) or later (called a delay) depending on the timing of light. This relationship is described by a “phase response curve”. Generally speaking, light exposure in the evening or early night will delay the clock, and light in the late night or early morning will advance the clock. Timeshifter uses this property of light to time the light exposure advice and ensure that you adapt as quickly as possible to new time zones.